have all the pins turned off; writing a 0xFE will turn port 0
on leaving all the other ports off. Therefore, two bytes are
sent over the I2C link: the address of the part (0x70) and a
byte which represents which I/O pin to enable as an output
or input. The RobotC programs are available on the Servo
Magazine website at (
www.servomagazine.com).

CONCLUSION

The RobotC programming software
and the use of the I2C bus expands the usage of the NXT
Brick to design more advanced robot controls, and opens
the door to non-robotic control functions as well. This
article has provided the means to expand the I/O of the
NXT. The integrated circuits we’ve used have additional
functions that weren’t mentioned but their specs can be
downloaded online — just Google for them.

With these expansion tools I now leave it to your
imagination to create more powerful NXT applications! SV

STEER WINNING ROBOTS

WITHOUT SERVOS!

Perform proportional speed, direction, and steering with
only two Radio/Control channels for vehicles using two
separate brush-type electric motors mounted right and left
with our mixing RDFR dual speed control. Used in many
successful competitive robots. Single joystick operation: up
goes straight ahead, down is reverse. Pure right or left twirls
vehicle as motors turn opposite directions. In between stick
positions completely proportional. Plugs in like a servo to
your Futaba, JR, Hitec, or similar radio. Compatible with gyro
steering stabilization. Various volt and amp sizes available.
The RDFR47E 55V 75A per motor unit pictured above.
www.vantec.com